Preemptive Overcalls
A preemptive overcall is a jump overcall (so 2♦ is preemptive over 1♣ but not over 1♥) that is otherwise identical to a preemptive opening bid.
The suit requirements for preemptive overcalls are generally similar to a preemtive opening. However, they are normally loosened in third seat, when the partner has already passed, so the opening bidder can be sure that the only side preempted are the opponents, and thus can bid with better or thinner values.
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